Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$44.50	6.111%	$47.2194	$47.22	$47.20	$47.20
Purchase #2	$12.87	5.542%	$13.5833	$13.58	$13.60	$13.60
Purchase #3	$69.82	12.209%	$78.3443	$78.34	$78.35	$78.30
Purchase #4	$182.83	4.411%	$190.8946	$190.89	$190.90	$190.90
Purchase #5	$160.66	5.234%	$169.0689	$169.07	$169.05	$169.10
Purchase #6	$45.87	9.625%	$50.285	$50.29	$50.30	$50.30
Purchase #7	$68.92	11.446%	$76.8086	$76.81	$76.80	$76.80
7 purchase totals =	$585.47		$626.2041	$626.20	$626.20	$626.20